A Sudanese driver for the World Food Programme (WFP) has been shot dead in war-torn South Kordofan state, the UN agency has said.
The attack on Sunday marks the second attack against the agency in two days.
Two gunmen opened fired on a UN car an estimated 80km north of the state capital Kadugli and killed the driver, a WFP spokesperson Amor Almagro told the AFP news agency.
Jamal Al Fadil Farag Allah, married with five children, is the first WFP employee to be killed in Sudan, according to Almagro.
"He was driving fellow staff member Saad Yousif when their vehicle was attacked by two unknown assailants," Almagro said.
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They were traveling in a marked UN vehicle on official business, she added.
Yousif was wounded but survived and was to be airlifted to Khartoum later on Sunday.
More than 200,000 refugees have fled a worsening humanitarian situation in South Kordofan and nearby Blue Nile states since fighting between government and rebel forces from the Sudan People's Liberation Movement-North (SPLM-N) began in June last year, the United Nations says.
Ethnic minority insurgents of the SPLM-N fought alongside southern rebels during Sudan's 22-year civil war, which ended in a 2005 peace deal and South Sudan's independence in July last year.
There are no figures for how many people have died since the war in South Kordofan and Blue Nile began.
The government of Sudan has placed tight restrictions on the operations of foreign relief agencies in the warzone, citing security concerns.
The killing on Sunday came two days after armed men in another part of the country spent about 12 hours looting and ransacking a WFP compound, Almagro said.
The WFP staff hid during the incident and were unhurt.
"Since the security situation remains tense and unpredictable we have decided to suspend our operation until the situation calms down," she said.
The WFP recently completed a food distribution to about 70,000 people in the area, meaning the suspension will not have an immediate impact on their food supply.
The attack against the WFP office came a day after a district chief died from gunshot wounds suffered in an ambush of his car in Kutum, raising tensions.
A Briton who worked for WFP in Nyala, South Darfur, was kidnapped earlier this year and spent nearly three months in custody before his release in May.